The present invention relates to ionic liquid epoxide compositions and their synthesis, and to ionic liquid epoxide monomers that form polymeric resins having desirable properties as adhesives, coatings, and composites.
Fabrication and repair operations inside spacecraft and other confined spaces require composites and adhesives that produce minimal or no harmful off-gassing products. Spacecraft additionally require structural components that must be prepared in and/or withstand harsh environments such as extreme temperatures, and hard vacuum.
Current epoxies, while significantly improved over earlier materials, tend to have off-gassing and flammability issues, especially in confined environments. Many cannot be handled in a space environment because hard vacuum and cryogenic temperatures cause them to rapidly evaporate and/or freeze. Even epoxy resins that are mixed and/or cured at ambient temperature ad pressure often do not perform well at cryogenic temperatures because they become brittle. Current aerospace epoxies have a lower service temperature limit of −45° F. as neat (unfilled) resins.
Adhesives and coatings comprising ionic liquids (ILs) that avoid the use of volatile organic compounds (VOC) as a solvent are known (US 2007/0194275 A1; US 2008/0017224 A1). Adhesives and coatings of this type having high tensile and adhesive strengths both at ambient temperatures as well as cryogenic temperatures, however, are not known. The present invention overcomes these limitations by providing IL epoxide monomers that react with cross-linking agents to form polymers exhibiting high tensile and adhesive strengths at extremely low temperatures. These properties make the polymers particularly well-suited for use in adhesives, coatings, composites, or articles of manufacture for use in harsh environments such as low temperatures and high physical stresses.